The present invention relates to a plasma processing apparatus and a plasma processing method for processing a substrate-like sample such as a semiconductor wafer disposed in a processing chamber disposed inside a vacuum vessel using a plasma generated in the processing chamber, and more particularly to a plasma processing apparatus and a plasma processing method for processing a sample by forming a high-frequency-bias potential on the sample using high-frequency power supplied to an electrode disposed inside a sample stage on which the sample is placed.
As one of the processes of fabricating semiconductor devices in prior art techniques, there has been used a technique for forming a circuit wiring structure using a plasma for etching a plurality of film layers including masks disposed on a surface of a substrate-like sample such as a semiconductor wafer. Examples of such prior art techniques using plasma include a plasma processing apparatus that generates plasma by an electron cyclotron resonance (hereinafter abbreviated as ECR).
The plasma processing apparatus for etching using plasma by the ECR introduces electric and magnetic fields for generating a plasma in a processing chamber disposed inside a vacuum vessel to excite the atoms or molecules of a process gas supplied into the processing chamber thereby to generate the plasma. Inside such an apparatus, electrons introduced into the processing chamber and moving in an electric field of a high frequency such as microwave and a VHF/UHF band are subject to cyclotron motion in a magnetic field also introduced thereinto. Thus, a plasma can be efficiently generated by selecting the magnetic field strength and the high-frequency electric field frequency so as to induce resonance in both electric and magnetic fields.
Further, in order to promote etching and achieve the processed shape with a desired high accuracy, it is common practice to supply high-frequency power to a metal electrode disposed inside a sample stage which is disposed in the processing chamber and on which the sample is placed so as to introduce charged particles in the generated plasma into a film layer for processing the sample to form a desired bias potential above the sample stage or an upper surface of the sample. The high-frequency power applied to the sample is hereinafter referred to as a high-frequency-bias power or simply referred to as a high-frequency bias.
The process gas to be introduced into the processing chamber and to be used for generating plasma is selected from the gasses that can efficiently process the film layer according to the material of the film layer to be processed, and generally a halogen gas such as chlorine and fluorine is widely used as such. The etching proceeds while charged particles such as particles or ions having high activity including radicals generated by the plasma react with the material of the film layer to be processed.
In such prior art, it has been common practice to appropriately control the supply of the high-frequency bias to achieve higher precision of the shape to be etched. For example, there has been known a technique of applying a modulated or intermittent high-frequency bias to an electrode disposed inside the sample stage. Further, there have been known a technique of modulating and supplying not only the high-frequency bias but also an electric field for generating plasma or power for generating plasma; and a technique of synchronizing the time of generation between the modulated and supplied plasma generation power (electric field) and the modulated and supplied high-frequency bias.
Further, a technique is disclosed in JP-A-2002-93781 in which supply of power for generating plasma or supply of high-frequency-bias power are intermittently repeated thereby to detect temporal changes indicated by characteristic values such as plasma density and strength in the transient state, and based on this, the sample processing is controlled or the plasma processing apparatus is diagnosed.